# Intersection of Two Arrays

## Question

Given two arrays, write a function to compute their intersection.

Each element in the result must be unique. The result can be in any order.

Example Given nums1 = [1, 2, 2, 1], nums2 = [2, 2], return [2].

## Solution

``````// HashMap Approach
public class Solution {
/**
* @param nums1 an integer array
* @param nums2 an integer array
* @return an integer array
*/
public int[] intersection(int[] nums1, int[] nums2) {
HashMap<Integer, Boolean> map1 = new HashMap<Integer, Boolean>();
HashMap<Integer, Boolean> intersectMap = new HashMap<Integer, Boolean>();
for (int i = 0; i < nums1.length; i++) {
if (!map1.containsKey(nums1[i])) {
map1.put(nums1[i], true);
}
}
for (int j = 0; j < nums2.length; j++) {
if (map1.containsKey(nums2[j]) && !intersectMap.containsKey(nums2[j])) {
intersectMap.put(nums2[j], true);
}
}
int[] result = new int[intersectMap.size()];
int i = 0;
for (Integer e : intersectMap.keySet()) {
result[i] = e;
i++;
}
return result;
}
}
``````
``````// Sort & Merge
public class Solution {
/**
* @param nums1 an integer array
* @param nums2 an integer array
* @return an integer array
*/
public int[] intersection(int[] nums1, int[] nums2) {
Arrays.sort(nums1);
Arrays.sort(nums2);

int i = 0, j = 0;
int[] temp = new int[nums1.length];
int index = 0;
while (i < nums1.length && j < nums2.length) {
if (nums1[i] == nums2[j]) {
if (index == 0 || temp[index - 1] != nums1[i]) {
temp[index++] = nums1[i];
}
i++;
j++;
} else if (nums1[i] < nums2[j]) {
i++;
} else {
j++;
}
}

int[] result = new int[index];
for (int k = 0; k < index; k++) {
result[k] = temp[k];
}

return result;
}
}
``````